Answer:
the probability that the part came from A given that the piece is defective is 1/2 (50%)
Step-by-step explanation:
defining the event A= getting a defective piece , Bi=getting a piece from the i-th supplier and Ci= getting a defective piece from the i-th supplier=1/3 (since each supplier is equally likely to be chosen)
P(A)= ∑P(Bi)*P(Ci) = 1/3* 0.003 + 1/3* 0.002 + 1/3* 0.001 = 1/3 * 0.006 = 0.002
then from the theorem of Bayes
P(Ca/A)=P(Ca ∩ A) / P(A) = P(Ca)/P(A) = 1/3*0.003 / 0.002 = 1/2
P(Ca/A)= 1/2 (50%)
then the probability that the part came from A given that the piece is defective is 1/2 (50%)